Leitch Pass-Through Implementation Notes

Leitch Pass-Through protocol for router control is supported in Helm, RouteMaster and RouteMaster VR.

Originally developed by Leitch Technology in 1999, the protocol is used by Harris and Imagine Communications routers. Other manufacturers like For-A also use variants of the protocol, with custom extensions. Modern Harris/Imaging routers use the more extensive Harris LRC protocol.

RouteMaster uses the protocol for both outgoing and incoming connections, allowing third-party systems using Pass-Through to control RouteMaster.  Helm uses it for outgoing connections to control routers.

Limitations

The standard Pass-Through protocol does not give access to mnemonics for router sources and destinations. Also, there is no way to query the Lock status of a destination.

FOR-A MFR-4000 series

The MFR-4000 series routers offer an extended version of the protocol which they refer to as “Crosspoint Remote Control 2”, This supports retrieval of source and destination names from the router. Helm and RouteMaster use this extension if the UseRouterNames property below is set to true.

The router must be configured via the web UI to enable the “Crosspoint Remote Control 2” protocol. Setting the Username and Password special properties is also required.

Use over TCP/IP

Originally designed as an RS-422 serial protocol, Pass-Through can also be used over TCP/IP. There is no standard port number for this.

When using over TCP/IP, the protocol often requires a login step, where a username and password are sent from client to router. This is poorly documented by Harris, and a common source of problems.

When controlling a router via this protocol, Helm and Routemaster will send username and password after a brief connection delay. They do not expect any login prompt from the router, and no checks are performed on the success of the login.  If the username is blank, this process is skipped.

From V2.5.0,  RouteMaster can send login: and password: prompts when emulating a Leitch router. This requires the Login Prompt option to be set in client configuration dialog. Any username and password sent are ignored by RouteMaster, but some systems won’t connect until they see the appropriate prompts.

Supported and Required Commands

This table details the commands used for outgoing connections, and the commands supported for incoming connections.

Command Outgoing Incoming Notes
Enable Reporting Yes RouteMaster always has reporting enabled
Request Level Status Yes Yes
Crosspoint Take Yes Yes
Lock/Protect/Unlock Yes Yes
Crosspoint Status Yes Yes

Special Properties

For outgoing connections, the following properties can be set directly in Helm Designer, or in the RouteMaster configuration file.

Username string Name of user to log in. If blank, no authentication is attempted
Password string Password for login
LoginDelay milliseconds Delay used before sending Username and Password at login. Default = 1000
ID integer ID to use for Panel Take and Lock/Unlock commands. Default is zero.
UseRouterNames Boolean If true, use the FOR-A extension to read source and destination names.